Typical turbine casings generally are formed with a number of sections that are connected to each other. The sections may be connected by bolted flanges in any orientation and similar arrangements. During a transient startup of a gas turbine, the horizontal joints may remain colder than the rest of the casing due to the additional amount of material required to accommodate the bolt. This thermal difference may cause the casing to be “out of roundness” due to the fact that the time to heat up the horizontal joint may be slower than that of the surrounding casing. This condition is also called ovalization or “pucker”. On shutdown, an opposite condition may occur where the horizontal joint remains hot while the casing around it cools off so as to cause the opposite casing movement or ovalization.
There is therefore a desire to reduce or eliminate the presence of thermal gradients that may cause an “out of roundness” about the joints of a casing for a rotary machine such as a turbine. Elimination of these thermal gradients should promote a longer lifetime for the equipment with increased operating efficiency due to the maintenance of uniform clearances therein.